MAINT: Pin gym[atari] version (#112)

* MAINT: Pin gym[atari] version

* Update CI image

* Update packages for default debian image

Author: melissawm

Diff for: .circleci/config.yml

@@ -6,14 +6,14 @@ jobs:
   build-docs:
     working_directory: ~/repo
     docker:
-      - image: circleci/python:3.8.5-buster
+      - image: cimg/python:3.8
 
     steps:
       - checkout
 
       - run:
           name: Install deps for building atari-py
-          command: sudo apt-get install -y cmake ffmpeg
+          command: sudo apt-get update && sudo apt-get install -y cmake ffmpeg
 
       - run:
           name: Install Python dependencies

Diff for: environment.yml

@@ -14,4 +14,4 @@ dependencies:
   - pooch
   - pip:
     - jupyter-book
-    - gym[atari]
+    - gym[atari]==0.19